Automated semiconductor processing system

ABSTRACT

An automated semiconductor processing system has an indexer bay perpendicularly aligned with a process bay within a clean air enclosure. An indexer in the indexer bay provides stocking or storage for work in progress semiconductor wafers. Process chambers are located in the process bay. A process robot moves between the indexer bay and process bay to carry semi-conductor wafers to and from the process chambers. The process robot has a robot arm vertically moveable along a lift rail. Semiconductor wafers are carried offset from the robot arm, to better avoid contamination. The automated system is compact and requires less clean room floor space.

This application is continuation-in-part of U.S. patent application Ser.No. 09/112,259, filed Jul. 8, 1998, which is a continuation-in-part ofU.S. patent application Ser. No. 08/994,737, filed Dec. 19, 1997 andentitled “Semiconductor Wafer Processing Apparatus Having Improved WaferInput/Output Handling System”, Express Mail No. EM425812465US, andincorporated herein by reference.

The field of the invention is automated semiconducted wafer processingsystems, used for processing semiconductor wafers, hard disk media,semiconductor substrates, and similar materials requiring very lowlevels of contamination.

BACKGROUND OF THE INVENTION

Computers, televisions, telephones and other electronic products containlarge numbers of essential electronic semiconductor devices. To produceelectronic products, hundreds or thousands of semiconductor devices aremanufactured in a very small space, using lithography techniques onsemiconductor substrates, such as on silicon wafers. Due to theextremely small dimensions involved in manufacturing semiconductordevices, contaminants on the semiconductor substrate material, such asparticles of dust, dirt, paint, metal, etc. lead to defects in the endproducts.

To exclude contaminants, semiconductor substrates are processed withinclean rooms. Clean rooms are enclosed areas or rooms within asemiconductor manufacturing facility, designed to keep out contaminants.All air provided to a clean room is typically highly filtered to preventairborne contaminants from entering into or circulating within the cleanroom. Special materials and equipment are needed to maintaincontaminants within the clean room at adequately low levels.Consequently, construction and maintenance of clean rooms can be timeconsuming and costly. As a result, the semiconductor processingequipment installed within a clean room should preferably be compact, sothat large numbers of semiconductor wafers can be processed within asmaller space, thereby reducing space requirements and costs.Accordingly, there is a need for smaller semiconductor processingequipment, to reduce clean room space requirements.

Existing automated semiconductor processing systems use robots to carrythe semiconductor materials. These robots are designed to avoid creatingparticles which could contaminate the semiconductors. However, even withcareful design, material selection, and robot operation, particles maystill be created by these robots, via their moving parts. Accordingly,there is a need for improved techniques for processing semiconductorsubstrate materials with very low levels of contamination to maintainthe level of defects at acceptable levels.

SUMMARY OF THE INVENTION

In a first aspect of the invention, an automated semiconductorprocessing system has an indexer bay or space and a process bay or spacewithin an enclosure. The indexer bay is oriented perpendicularly to theprocess bay, to form a compact design requiring less floor space in aclean room.

In a second separate aspect of the invention, an indexer is provided inthe indexer bay. The indexer preferably holds pallets for supportingsemiconductor wafers contained within cassettes. Pallet movers in theindexer move the pallets and cassettes in sequence from an indexerloading position, through a plurality of intermediate storage positions,to an indexer unload position. The indexer allows the automatedsemiconductor processing system to run continuously, by moving andstoring cassettes.

In a third separate aspect of the invention, the pallet movers includean x-axis and y-axis shift system, for moving pallets longitudinally andlaterally around in the indexer. Preferably the y-axis shift system hasa pair of toothed belts engaging a rack on the bottom of the pallets, toprevent inadvertent movement of the pallets relative to the belts.

In a fourth separate aspect of the invention, prisms on the palletsredirect light beams from sensor pairs, to detect the presence orabsence of a cassette on a pallet, or wafers in a cassette.

In a fifth separate aspect of the invention, a process robot within anautomated semiconductor processing system has a robot arm verticallymoveable along a lift rail. The robot arm has a forearm segmentextending between an elbow joint and a wrist joint. A wafer holder onthe robot arm is laterally offset from the elbow and wrist joints. Therobot arm is compact yet has an extended range of travel. The processingsystem therefore requires less space.

In a sixth and separate aspect of the invention, a moveable buffer shelfis positioned over the indexer, to increase productivity and versatilityof the system.

In a seventh and separate aspect of the invention, a novel processmodule door is provided to better close and seal a process modulechamber.

In a eighth aspect of the invention, two or more of the featuresdescribed above are combined to provide an improved automatedsemiconductor processing system.

It is an object of the invention to provide an automated semiconductorprocessing system, better designed to keep semiconductor wafers free ofcontaminants. It is a further object of the invention to provide anautomated semiconductor processing system that is versatile, yetcompact, to reduce clean room space requirements.

Other objects, features and advantages will appear hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the same reference number denotes the sameelement throughout the several views:

FIG. 1 is a top, rear and left side perspective view of the presentautomated semiconductor processing system;

FIGS. 2 and 3 are front, top, and left side perspective views thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a front perspective view of the input/output robot shown inFIG. 3;

FIG. 7 is a rear perspective view thereof;

FIG. 8 is a perspective view of the indexer shown in FIGS. 1-3, withvarious components removed for clarity of illustration;

FIG. 9 is a perspective view thereof with additional components removedfor clarity of illustration;

FIG. 10 is yet another perspective view thereof showing additionaldetails;

FIG. 11 is a leftside view of the indexer shown in FIGS. 1-3;

FIG. 12 is a plan view thereof, with the pallets on the indexer removed,for clarity of illustration;

FIG. 13 is a front view of the indexer shown in FIGS. 1-3;

FIG. 14 is a plan view of the indexer shown in FIGS. 1-3, andillustrating sequences of movement;

FIG. 15 is a perspective view of the elevator shown in FIG. 5, in thelowered position;

FIG. 16 is a perspective view thereof showing the elevator in the raisedposition;

FIG. 17 is a front perspective view of the process robot shown in FIGS.2 and 5;

FIG. 18 is a plan view thereof;

FIG. 19 is an enlarged plan view thereof;

FIG. 20 is a rear perspective view of the process robot, with the armfully withdrawn;

FIG. 21 is a plan view thereof;

FIG. 22 is a side elevation view, in part section, of the process robot;

FIG. 23 is a front perspective view of the process robot;

FIGS. 24A-24E are schematic illustrations showing various positions ofthe arm of the process robot;

FIG. 25 is a perspective view of a process module, as shown in FIGS.3-5;

FIG. 26 is a perspective view of the semiconductor process moduleillustrated in FIGS. 4, 5 and 25, and having a novel door actuation andsealing mechanism;

FIG. 27 is a perspective view of the process module door actuationassembly;

FIG. 28 is a cross-sectional side view of the process module door in anopen position;

FIG. 29 is a cross-sectional side view of the process module door in aclosed position;

FIG. 30 is a perspective view of a second indexer embodiment; and

FIG. 31 is a reversed perspective view of the indexer shown in FIG. 30,with various components removed, for purposes of illustration.

DETAILED OF DESCRIPTION OF THE DRAWINGS

OVERVIEW

Turning now in detail to the drawings, as shown in FIGS. 1-5, anautomated semiconductor material processing system 50 is installedwithin a clean room 52. The system 50 has a clean air enclosure orhousing 54 having a left side wall 56 with a fixed transparent window 57to allow viewing of operations within the enclosure 54. Similarly, theenclosure 54 has a front wall 58, as shown in FIG. 2, having a fixedtransparent window 59.

A loading/unloading opening 60 in the front wall 58 is closed off duringoperation of the system 50 by a transparent loading window or panel 62,as illustrated in FIG. 2. Referring to FIGS. 1-5, down draft fans orblowers 80 are provided on top of the enclosure 54, to continuously moveclean air room downwardly through the enclosure. A utilities compartment82 provides space for power supplies, reagent tanks, pumps, and othercomponents well known for semiconductor processing.

A user interface 64, on the front wall 58 provides information andinputs control instructions from the system operator. The user interfaceis linked to a computer/controller 85, in the utilities compartment 82,or at a remote location. The computer/controller 85 is linked to thevarious motors and sensors described below, as well as to a facilitycontrol computer, to control operation of the system 50.

Referring to FIGS. 1-4, and especially to FIG. 3, the system 50 includesan indexer bay or space 75 extending rearwardly along the left side wall56. A process bay or space 94 extends along the front wall 58,perpendicularly to the indexer bay 75. The indexer bay or space 75, anda process bay or space 95 are continuous with each other, and aredesignated and illustrated schematically in FIG. 3, as separate spacesonly for purposes of description. Referring to FIGS. 1-5, theloading/unloading window 60 opens through the front wall 58 of theenclosure 54 into the indexer bay 75. An I/O robot 86 in the indexer bay75 is located largely below the opening 60.

An indexer 72 is provided in the indexer bay 75, generally in alignmentwith the opening 60. An input plate 132 on the indexer 72 extends overthe I/O robot 86 toward the window 60. The indexer 72 preferably holdsup to eight cassettes 88 containing flat media, e.g., silicon wafers 90.The cassettes 88 rest on pallets 136 on the indexer 72. The pallets 136and the I/O plate 132 are vertically positioned at about the sameelevation as the bottom of the opening 60. A moving buffer shelf 76 issupported above the cassettes 88 on the indexer 72 via a vertical bufferplate 130 extending up from a center beam in the indexer 72.

Referring to FIGS. 2, 3 and 4, the process bay 95 includes two or moreprocess chambers. In the embodiment shown, the process chambers are achemical process chamber 68, and a spin/rinser dryer 70. A process robot66 moves through the process bay 95 to the indexer 72, to carry wafers90 to or from the chambers 68 or 70.

Referring to FIGS. 3 and 5, and momentarily to FIGS. 15 and 16, anelevator 78 under the indexer 72 lifts the wafers 90 out of thecassettes 88 (2 cassette loads at a time) so that they can be picked upand carried by the process robot 66. As shown in FIG. 16, each cassette88 preferably holds 25 wafers, with the eight cassette capacity of theindexer 72 holding 200 wafers. The wafers are handled in batches of 50,as the elevator 78 and process robot 66 carry the combined contents oftwo cassettes simultaneously.

THE I/O ROBOT

Referring to FIGS. 6 and 7, the I/O robot 86 has a mounting plate 110attached to the left side wall 56 or adjacent enclosure structure. AY-axis rail 112 is supported on the mounting plate 110. A linearactuator 114 on the rail 112 moves an armature 105 in the Y direction,as shown in FIGS. 3 and 6.

Referring to FIG. 7, an X-axis rail 106 on the back of the armature 105supports a Z-axis or vertical fork rail 102. A vertical fork actuator104 moves the rail 102 vertically on the armature 105. An x-axisactuator 108 moves the vertical rail 102, along with the verticalactuator 104, in the X or lateral direction. A cassette fork 100 nearthe top of the vertical rail 102 is adapted to lift a cassette 88 byengaging the cassette side flanges 89.

THE INDEXER

Turning now to FIG. 8, the indexer 72 has a rectangular frame 118including a bottom plate 120, a front plate 122, a back plate 124, andleft and rightend plates 126 and 128. The I/O plate 132 is attached tothe right end plate 122, and braced by gussets 134. A center beam 160divides the indexer into an input row or side 135 and an output row 137.The vertical buffer support plate 130 is positioned and moves back andforth within a centrally located buffer plate slot 144 in the centerbeam 160. Two pairs of opposing pallet rails 142 extend substantiallyfrom the left end plate 126, to the right end plate 128, and provideresting or supporting surfaces for the pallets 136 at the pallet deck orsurface 139. Referring momentarily to FIG. 14, the indexer 72 includes10 pallet positions: A, B, C, D, E, F, G, H, I, and J. The indexer 72has eight pallets 136, so that two positions, at diagonally oppositecorners, are always vacant. Turning to FIG. 12, cutouts 162 in thebottom plate 120 of the indexer 72, at positions C and H, allow air toflow downwardly through the indexer 72. Elevator clearance holes 164through the bottom plate 120, at positions I and J, provide clearancefor the elevator 78.

Referring still to FIGS. 8-14, the indexer 72 includes a X-axis orlateral shift system or assembly generally designated 140, and alongitudinal or a Y-axis shift system or assembly, generally designated170. These shift systems move the pallets 136 carrying the cassettes 88around on the indexer 72, as shown in FIG. 14.

As best shown in FIG. 9, the lateral shift system 140 includes a lateralguide block 150, fixed to the indexer frame 118. A lateral shift endfork 146A is supported on the lateral guide block 150, and is driven bya lateral drive motor 154 to step or sequence between positions E and F,as shown in FIG. 14. An end fork air cylinder 152 raises and lowers theend fork 146A between fixed up and down positions which are fixed bymechanical stops. FIGS. 9 and 10 show components of the lateral shiftsystem 140 at the left or inside end of the indexer 72. Similar orduplicate components (the lateral guide block 150; an end fork 146B anda lateral air cylinder 152) are mounted at the right end as well. Alateral shift system linking belt 156 extends around the perimeter ofthe indexer frame 118, supported by idlers 157, and is attached to thediagonally opposite end forks 146A and 146B. When the lateral drivemotor 154 is energized, end fork 146A moves from position F to positionE, while end fork 146B simultaneously moves from position A to PositionJ, and vice versa.

Referring still to FIGS. 8-14, the longitudinal or Y-axis shift assembly170 of the indexer 72 includes longitudinal guide rails 172 extendingparallel to the front and back plates 122 and 124, on either side of thecenter rail 160. Eight side forks 180B-180J are located at positions B,C, D, E, G, H, I, and J, as best shown in FIG. 12. A side fork actuatoror air cylinder 174 is attached to each of the eight side forks 180. Theair cylinders 174 are longitudinally displaceable with the side forks180, as they move back and forth on the longitudinal guide rails 172.The eight side forks 180 are joined together by a longitudinal drivebelt 178. The longitudinal drive belt 178 extends in a loop around theperimeter of the indexer frame 118, supported on idlers. Thelongitudinal drive belt 178 is positioned within the indexer frame 118vertically above the lateral drive belt 156. A longitudinal or Y-axisdrive motor 176 is engaged to the drive belt 178, such that withactuation of the motor 176, all eight side forks 180 movesimultaneously. Referring to FIG. 12, when the motor drives side forks180B-180E in the input row 135 in direction I, the side forks 180G-180Jon the opposite side of the center beam 160B, in the output row 137,move in direction O.

Referring to FIGS. 8-11, the indexer 72 also includes a buffer shelfshift system or assembly, generally designated 190. The buffer shiftsystem 190 shifts the vertical buffer plate 130, which supports thebuffer shelf 76 from the front position shown in FIG. 9 to the rearposition shown in FIG. 8. The buffer shelf 76, shown in phantom in FIG.8 is omitted from the other figures, for clarity of illustration.

Referring primarily to FIG. 10, the buffer shift system 190 includes abuffer drive motor 198 linked to a buffer drive belt 200 through a flexcoupling 196, and a buffer capstan 192. The buffer drive belt 200extends around the capstan 192 and a buffer belt idler 194, positionedat opposite ends of the buffer plate slot 144. The vertical buffer plate130 is secured to the buffer drive belt 200. The bottom end of thevertical buffer plate 130 is slidably attached to a buffer plate guiderail 202 underneath the buffer plate slot 144.

The indexer 72 has three sets of sensors 138 at each location A-J. Thethree sensors at each location may be separate individual sensors, or asingle combination sensor. The sensors, at each position, sense whethera pallet is present; whether a cassette is present on a pallet; andwhether wafers are present in a cassette. The sensors are linked to acontroller or computer and provide status information for each locationin the indexer 72. Preferably, optical sensors are used.

Turning now to FIGS. 15 and 16, the elevator 78 has a motor 210 linkedto an armature 212 through a lead screw or other rotation to lineardrive. Wafer platforms 216 are supported on lift columns 214. Actuationof the motor 210 lifts the armature 212 up along a elevator rail 215, tovertically move the wafers 90 into and out of the cassettes 88. With thewafers 90 lifted out of the cassettes 88 as shown in FIG. 16, they canbe picked up by the process robot 66.

THE PROCESS ROBOT

Turning now to FIGS. 17-23, the process robot 66 includes a lateral orX-axis rail 250 extending through the process bay 95 and partially intothe indexer bay 75. A lift unit 252 is moveable along the lateral rail250, driven by a magnetic flux linear drive motor 251. A robot arm, 255,is attached to a vertical lift rail 254 on the lift unit 252. An A/Clift motor 257 moves the robot arm 255 vertically along the lift rail254. As shown in FIG. 23, the cylinder 280 of a gas spring counterbalance 278 is attached to the robot arm 255. A piston 282 extending outof the cylinder 280 is attached to the lift unit 252. The gas springcounterbalance 278 exerts a constant upward force on the robot arm 255,to reduce the lifting or braking force that the lift motor 257 mustexert to move or position the robot arm 255.

Referring still to FIGS. 17-23, the robot arm 255 has an elbow drive A/Cmotor 259 within an elbow housing 258. The elbow housing 258 is attachedto the slide of the lift rail 254, on the lift unit 252. A forearm 260is attached to the elbow housing 258 via an elbow joint 256. The forearm260 is mechanically coupled to the elbow drive motor 259 via a gearreduction 261.

A wrist drive A/C servo motor 265 is contained within a wrist housing264 pivotably attached to the outer end of the forearm 260 via a wristjoint 262. A wafer holder 268 formed by opposing end effectors 270 isjoined to the lower front area of the wrist housing 264. Grooves 274 inthe end effectors 270 facilitate engaging, lifting and carrying thewafers 90. A remote camera head 266 positioned on top of the wristhousing 264, and linked to the computer/controller 85, views thepositions of the rotor retainers within the process chambers (asdescribed in U.S. patent application Ser. No. 08/623,349, incorporatedherein by reference). The computer/controller can then determine whetherthe process robot can properly insert the wafers into the processchamber. The camera head 266 is also used to verify that the rotorrotainers are fully locked before processing begins within the processchamber.

Motor amplifiers 275, for driving the wrist drive motor 265, elbow drivemotor 259, lift motor 257, and lateral drive motor 251, are contained inand move with the lift unit 252. Locating the motor amplifiers in thelift unit 252 reduces space requirements and cabling requirements.

THE PROCESS MODULE

Turning now to FIG. 25, a process module 300 in the process bay 95includes, for example, the spin rinser dryer 70 and the chemical processchamber 68, although other modules, or additional modules may be used.End effector rinser dryers 302 are provided in the front floor 305 ofthe process module 300.

Referring to FIGS. 26-29, the process module 300 includes a processvessel 310 which partially encloses a process bowl 314. The processvessel 310 mates with a movable door 512 which can be moved between theclosed position shown in solid lines in FIG. 26, and an open positionshown in phantom outline.

Referring to FIGS. 26 and 27, the door assembly 500 is aligned in afixed position parallel to a front wall 502 of the process vessel 310.

The door assembly 500 includes a door plate 510 supporting a door 512and a door actuator 514 generally designated 514. The door 512 includesa stiffening plate 504 having a viewing window 508 that permits visualinspection of the processing bowl or chamber 314. The door actuator 514includes a stationary outer cylinder 516 coupled to the door supportplate 510, and an extension ring 518. The extension ring 518 isconcentrically and slidably positioned inside of the outer cylinder ring516. The door support plate 510 includes a viewing aperture 520, whichaligns with the window 508, when closed, for providing visibility intothe processing chamber.

Referring to FIGS. 26 and 27, the door support plate 510 is attached oneach side to slideable guide brackets 522. Each guide bracket 522 isslidably mounted to a pneumatic cylinder 524. The cylinders 524 areconnected to the front wall 502 of the processing vessel via mountingplates 528. The combination of the guide brackets 522, the cylinders524, and the mounting plates 528 provides a rigid door mountingconstruction that needs no additional guides or support blocks. Theguide brackets 522 are mounted for substantially vertical movement sothat the door assembly can be moved between an open position to allowaccess into the bowl of the processor, and a closed position wherein thedoor assembly is in substantially concentric alignment with the bowl314. In the closed position, the door can be extended and sealed againstthe bowl 314 of the processor.

Referring to FIGS. 28 and 29, an annular inner hub 530 has an annularflange 532 and a cylinder 534. The annular flange 532 is attached to thedoor support plate 510. A plurality of fasteners secure the outercylinder ring 516 and the annular flange 532 concentrically to themounting plate 510.

The extension ring 518 is concentrically positioned between the hub 530and the outer cylinder ring 516, and includes a U-shaped portion 519that defines an annular guide receptacle 520. The cylinder 534 fitswithin the annular guide receptacle 520. The extension ring 518 alsoincludes an annular end face 540, as shown in FIG. 28. The extensionring 518 is displaceable with an annular chamber 542 defined by thecylinder 534 and the other cylinder ring 516, to seal and unseal thebowl 314.

The extension ring 518 bifurcates the chamber 542 into two operativecompartments: a retraction chamber 543 and an extension chamber 544.Each chamber is adapted to hold pneumatic or hydraulic fluid and act aspneumatic or hydraulic cylinder. Multiple annular seals 550 arepositioned on or against the extension ring 518 to seal the chambers 543and 544.

Separate fluid supply conduits are preferably provided to the retractionchamber 543 and the extension chamber 544 to increase or decrease fluidpressure within the respective chambers and effectuate movement of theextension ring 518. As shown in FIG. 28, when hydraulic fluid issupplied to the extension chamber 544, the extension ring 518 moves awayfrom the door support plate 510. Movement of the extension ring 518 intothe extended position shown in FIG. 28 moves the door 512 into sealingengagement with the access opening 506 of the processor bowl, therebysealing the process module 300.

An annular door seal 551 is mounted on the periphery of the door 512.The door seal includes a lip 552 and a tongue 554. When the door is inthe closed position shown in FIG. 28, the lip 552 of the door seal liesin a plane that is within the front wall of the processor, and thetongue presses in sealing engagement against the outside rim of theprocess bowl 314 thereby making a seal between the door 512 and theprocess bowl 314. The door seal also preferably includes a flange 555which acts as a stop for the door seal.

The combination of the extension ring 518 and the door seal 550 providesa highly reliable and effective door closing and sealing mechanism.Piston-like movement of the ring 518 allows it to move the door 512straight outwardly from the support plate without bowing or bending, andwithout the need for peripheral adjustments to ensure smooth movement.By seating against the outside rim of the process bowl, the tongueprovides an effective fluid tight seal and automatically compensates forany misalignment between the door and the processor.

The inner hub 530 and the outer cylinder ring 516, are rigidly attachedto the door plate 510. The door plate, in turn, is fixed relative to theprocess bowl 514, via the connection of the door plate 510, to thecylinders 524, to the front wall 502. Consequently, as the extensionring 518 moves outwardly away from the door plate 510, it can presstightly against and seal the bowl 514.

OPERATION

In use, the operator of the system 50 initiates a loading sequence byentering commands via the user interface 64. The window panel 62 dropsdown, thereby opening the loading window 60. The operator places acassette 88 filled with wafers 90 onto the I/O plate 132. The cassette88 may be initially placed on the I/O plate 132 by a human operator orby another robot. The cutout 133 in the I/O plate positions the cassette88, so that it may be lifted by the I/O robot, and also allows air toflow downwardly over the wafers 90 in the cassette 88.

The fork 100 of the I/O robot 86 is initially in the same X-Y positionas the I/O plate 132. The vertical fork motor or actuator 14 raises thefork 100, until the fork has engaged the side flanges 89 of the cassette88. The I/O robot 86 then lifts the cassette 88 vertically off of theI/O plate 132, shifts laterally (in the X direction) towards the leftside wall 56, via actuation of the lateral motor 108. This movementaligns the now lifted cassette with the input row of the indexer. TheI/O robot 86 then moves the lifted cassette longitudinally (in theY-direction) toward the indexer, until the cassette is aligned above apallet in position A, via the Y-axis motor 114. The I/O robot then setsthe cassette 88 down on the pallet 136 at position A on the indexer 72.If there is no pallet at position A, the indexer 72 must first besequenced, as described below, to bring a pallet into position A. TheI/O robot then returns the fork 100 to its initial position.

With a first cassette 88 resting on a pallet 136 at position A, which isthe cassette loading position, the longitudinal shift system 170 movesthe side forks 180B-J (in the direction of arrow O in FIG. 12) until theside fork 180B is underneath the pallet 136 and cassette 88 in positionA. The end forks 146A and 146B have down or at-rest positions below thedown or at-rest positions of the side forks 180B-J, so that the sideforks 180B, 180E, 180G, and 180J can move into the end positions A, E, Fand J, without interfering with the end forks 146A and 146B. As all ofthe side forks 180B-J are attached to the longitudinal drive belt 178,they all necessarily move together in the Y direction.

With the side fork 180B underneath the first cassette 88 in position A,the eight side fork air actuators or cylinders 174 are extended, causingthe side forks 180 to lift the pallets above them up and off of thepallet deck 139 With the pallets in the up position, the longitudinaldrive motor 176 turns in the opposite direction, moving side fork 180B,now carrying the first cassette 88 on a pallet, from position A toposition B. The air cylinders 174 are then retracted to lower the pallet136 and cassette 88 down into position B. After this movement iscompleted, there is no pallet at position A. As all of the side forkactuators 174 are controlled to move simultaneously, all of the sideforks 180B-J necessarily move together in the vertical Z-axis direction.

To continue loading or sequencing the indexer 72, the longitudinal drivemotor 176 is again energized to move side fork 180B back towardsposition A, and thereby move side fork 180J from position J back toposition I. During this movement, the side fork air cylinders 174 aredown, so that there is no pallet movement. Rather, the side forks aremerely repositioned below the pallets. The side forks are moved, in thisstep, enough to avoid interfering with the end forks, and notnecessarily one complete position. With the side fork 180) now clear ofposition J, the lateral drive motor 154 is energized to move the endfork 146B from position A to position J, and to simultaneously move theend fork 146A from position F to position E. Once under position J, thelateral air cylinders 152 are extended, lifting end fork 146B, and thepallet at position J, and simultaneously lifting end fork 146A to liftthe pallet at position E. The lateral drive motor 154 is then energizedin the reverse direction (direction L in FIG. 12) and via the lateralbelt 156, the end fork 146B carries the pallet from position J toposition A, and simultaneously, the end fork 146A carries a pallet fromposition E to position F. The lateral air cylinders 152 are thenretracted, to lower the pallets into positions A and F on the indexerdeck 139.

With a second pallet in position A, the indexer 72 is ready to receive asecond cassette 88. After a second cassette is positioned on the I/Oplate 132, the I/O robot 86 repeats the indexer loading sequence ofcassette movements, so that the second cassette is placed on the indexerat position A.

The foregoing sequence of steps is repeated until a cassette is loadedonto each of the eight pallets in the indexer. As the indexer has tenpositions A-J, and eight pallets, two diagonally opposite cornerpositions, either positions A and F, or positions E and J, will, at anygiven time, not have a pallet.

After the first and second cassettes 88 loaded into the indexer 72arrive at positions I and J, the elevator 78 is energized, lifting thewafer platforms 216 on the lift columns 214 up through the open bottomof the cassettes 88. The wafers 90 in the cassettes are lifted to anelevated access position, as shown in FIG. 16, where they are now readyto be picked up by the process robot 66.

The window panel 62 moves up to close off the loading window 60, toprevent an operator from inadvertently coming into contact with movingcomponents within the enclosure 54.

Referring now to FIGS. 20, 21 and 24B, the process robot 66 moves tolift the wafers 90 off of the elevator 78. Specifically, the lateraldrive flux motor 251 moves the lift unit 252 laterally until the waferholder 268 is properly aligned with the wafers 90 on the elevator 78.With appropriate control of the lift motor 257, the elbow drive motor258, and the wrist drive motor 265, the wafer holder 268 is moved inuntil the end effectors 270 are positioned and aligned on either side ofthe wafers 90, with the grooves 274 in the end effectors 270 eachaligned to receive a wafer. As shown in FIG. 24B, this wafer engagementmovement is an underhanded movement of the robot arm 255. The waferholder 268 is moved up to lift the wafers 90 off of the elevator 78. Therobot arm 255 then withdraws to the position shown in FIG. 24C. As theforearm has a 370° range of movement, and robot arm 255 is offset fromthe lift unit, the robot arm can be fully backed away from the indexer,with only minimal clearance space required, as shown in FIGS. 20 and 21.By appropriate control of the motors in the robot arm, the wafers aremaintained in a vertical or near vertical position.

To deliver the wafers 90 to a process chamber, the lateral drive motor251 is energized to move the lift unit 252 so that the wafers in thewafer holder 268 are brought into alignment with the selected processchamber. The robot arm 255 is raised up on the lift unit by the liftmotor 257. In addition, the forearm 260 is pivoted upwardly via theelbow drive motor 259. Simultaneously, the wrist drive motor 265 isdriven in an opposite direction to bring or maintain the wafer holder inan approximately 10° down incline orientation, as shown in FIG. 22.Using an overhand movement, as shown in FIG. 24A, the forearm is pivoteddownwardly to extend the wafer holder carrying the wafers into theprocess chamber. The robot arm 255 then withdraws from the processchamber.

To clean the end effectors 270, the wrist drive motor 265 is controlledto orient the end effectors vertically, as shown in FIG. 24D. With theend effectors aligned with the end effector rinser/dryer 302, the liftmotor 257 lowers the entire robot arm 255, to extend the end effectorsinto the end effector rinser/dryer 302. After the end effectors 270 arecleaned and dried, they are withdrawn from the end effector rinser/dryer302 and positioned to remove wafers from either process chamber, or topick up additional batches of wafers from the indexer for delivery to aprocess chamber. As the end effectors are cleaned at the process chamberrather than at another location, processing time can be reduced, becausethis cleaning step is accomplished without the need to move the processrobot.

As is apparent from e.g., FIG. 23, the wafer holder 268 is offset to oneside of the wrist joint 262 and elbow joint 256, as well as the othercomponents of the process robot 66. No part of the process robot 66 isever positioned directly above the wafers. As air is blown downwardly inthe enclosure 54, any particles generated or released by the processrobot 66 will not come into contact with the wafers. As a result, thepotential for contamination of the wafers during processing is reduced.

Referring to FIGS. 24A-24E, the process robot 66 has an elbow joint 256and a wrist joint 262, joined by a single segment or forearm 260.Consequently, in contrast to earlier known systems having shoulder,elbow and wrist joints, joined by two arm segments, the process robot 66achieves a range of vertical reach via movement of the robot arm 255 onthe lift rail 254, rather than by articulation of arm segments. Thisallows the process robot 66 to be very compact, while still achievingsufficient ranges of movement. Correspondingly, the entire enclosure 54can be made more compact.

As the process robot 66 can perform both underhanded and overhandedmovements, the vertical travel necessary on the lift rail 254 islimited. In addition, the ability to perform both underhanded andoverhanded movements allows the forearm 260 to be relatively short,which also contributes to a compact enclosure 54. to Referring to FIGS.1 and 16, the buffer shelf 76 moves forward (in direction O in FIG. 17)when the elevator 78 is in the down position, to receive up to 50wafers. The buffer shelf 76 holds the wafers until the appropriate emptycassette 88 is moved into the I and J positions, so that the processrobot 66 can move the disks from the buffer shelf 76 into the cassettesat positions I and J. When the buffer shelf 76 is not being loaded orunloaded with wafers, it remains in the back position (moved indirection I), so as not to interfere with operation of the elevator 78.The buffer shelf 76 temporarily holds already processed wafers, so thatthe process robot 66 can access and move the next batch of wafers forplacement into the process chambers, before off loading alreadyprocessed wafers back into the indexer. This ensures that the processchambers are constantly supplied with wafers for processing.

SECOND INDEXER EMBODIMENT

As shown in FIGS. 30 and 31, a second embodiment indexer 600 includes abox frame 602 formed by side walls 604 and 606, a front end wall 608,and a back end wall 610, joined to each other, and to a base plate 612.An input plate 614 extends outwardly from the front end wall 608. Acenter wall 616 and lateral ribs 666, divide the indexer 600 into firstand second rows R1 and R2, with each row having 5 pallet positions orstations, i.e., A-E and F-J, as shown in FIG. 12. The center wall 616 issupported in the box frame 602 via support bars 615 extending from thecenter wall 616 to the side walls 604 and 606.

Referring to FIG. 30, a buffer assembly 618 includes a buffer side plate620 attached to the inner side wall 606. A buffer tray 622 has combs 624on comb arms 626. The buffer tray 622 is supported on a buffer traysupport 630. The tray support 630 in turn is slidably mounted on upperand lower buffer rails 632 and 634, on the buffer side plate 620. Linearbearings 636 on the tray support 630 allow for low friction movement ofthe tray support 630 along the rails 632 and 634.

A buffer drive belt 642 extends around a buffer drive motor 638 and anend pulley 640. The buffer drive belt 642 is attached to the buffer traysupport, so that rotational movement of the motor 638 causestranslational (y-axis) movement of the buffer tray support 630 along therails 632 and 634. Locating the buffer assembly 618 on the side of theindexer 600, as shown in FIG. 30, allows for a more compact design, incomparison to the centrally located buffer assembly of the first indexerembodiment 72 shown in FIG. 8.

Referring to FIGS. 30 and 31, the indexer 600 includes a longitudinal ory-axis shift assembly, generally designated 650, and a lateral or x-axisshift assembly, generally designated as 652.

Referring to FIG. 31, the y-axis shift assembly 650 includes 2 side byside and parallel y-axis frames 660. Each y-axis frame 660 includes aninner frame plate 662, adjacent and attached to the center wall 616, andan outer frame plate 664, supported on the side walls 604 and 606. Thelateral ribs 666 are attached to and extend between the inner frameplate 662 and outer frame plate 664, in both of the y-axis frames 660.

End rollers 674 are rotatably mounted at the ends of each of the innerand outer frame plates 662 and 664 (for a total of 8 end rollers 674).Idler rollers 676 are spaced apart and rotatably mounted on the frameplates 662 and 664, between the end rollers 674, on each frame plate 662and 664. An endless toothed belt 670 is mounted over the end rollers 674and idler rollers 676 on each frame plate 662 and 664 (for a total of 4endless toothed belts 670). The teeth 672 on the belts 670 faceoutwardly, so that the smooth inside or back surface of the belts 670contact the end rollers 674 and idler rollers 676. While forillustration purposes, the teeth 672 are shown only at sections of thebelts 670, the belts 670 actually have continuous teeth 672 all around.In addition, for illustration purposes, the rollers and belt in theforeground of FIG. 31 have been omitted from the drawing.

Referring still to FIG. 31, a y-axis drive motor 680 supported on thecenter wall 616 is linked or engaged to a gear unit 682, which turnsdrive shafts 684A and 684B (in the side by side parallel y-axis frames660) at equal speeds, but in opposite directions. The drive shafts 684Aand 684B turn drive sprockets 686, which in turn drive the belts 670.The outside toothed surface of the belts 670 wraps around the drivesprockets 686, and around an idler sprockets 688, as shown in dottedline in FIG. 31.

As shown in FIG. 31, an x-axis sensor pair 690, and a y-axis sensor pair696, is provided at each of the ten pallet stations or locations A-J,delineated by the lateral ribs 666. The x-axis sensor pair includes aninfrared transmitter 692 and an infrared detector 694, laterally alignedwith each other (on a line perpendicular to the frame plates 662 and664). Similarly, the y-axis sensor pair 696 includes a y-axis infraredtransmitter 698 and a y-axis infrared detector 700, located generallycentrally on the lateral ribs 666, and aligned with each other (on aline parallel to the frame plates 662 and 664).

A reflective optical sensor 702 is provided in the side walls 604 and606, at each of the pallet positions A-J. The sensor pairs 690 and 696and optical sensor 702 are linked to the controller 85, which monitorsand controls operations of the indexer 600.

Referring back to FIG. 30, 8 rectangular pallets 710 are provided ineach row R1 and R2 of the indexer 600, so that four of the palletpositions in each row are always occupied by a pallet 710, and one endposition adjacent to end wall 608 or 610 is always open. Each pallet 710has a rectangular pallet cutout or opening 712. Pallet tooth racks 715,shown in dotted line in FIG. 30, are provided on the bottom surface ofthe pallets 710. The tooth rack 715 extends along both of the longersides of the pallet 710. The tooth rack 715 has teeth matching the sizeand pitch of the teeth 672 on the belts 70. Consequently, when a pallet710 is placed on a y-axis frame 660, the teeth on the pallet tooth rack715 positively engage the teeth 672 on the belts 670, so that the palletis substantially locked against y-axis movement relative to the belts670.

Each pallet 710 has a pair of x-axis and y-axis prisms. Specifically, anx-axis transmitter prism 714 is longitudinally aligned with an x-axisdetector prism 716, on each pallet 710, as shown in FIG. 30. Similarly,a y-axis transmitter prism 718 is laterally aligned with a y-axisdetector prism 720, on each pallet 710. With the pallet 710 in any oneof the ten pallet positions A-J in the indexer 600, the x-axistransmitter prism 714 and x-axis detector prism 716 are verticallydirectly above or aligned with the x-axis infrared transmitter 692 andx-axis infrared detector 694, respectively, in that pallet position.Similarly, the y-axis transmitter prism 718 and y-axis detector prism720 are vertically directly above and aligned with the y-axis infraredtransmitter 698 and the y-axis infrared detector 700, in that palletposition.

Referring to FIG. 31, the idler rollers 676 have roller flanges 678which protrude vertically above the belts 670. The roller flanges 678fit into roller grooves 675 (shown in dotted line in FIG. 30) on thebottom surface of each pallet 710. The engagement of the roller flanges678 into the grooves 675 prevents any x-axis movement of the pallets 710(unless the pallet 710 is lifted vertically.) Accordingly, the pallets710 are vertically supported on both the belts 670 and roller flanges678.

The indexer 600 has an x-axis shift assembly 652 substantially the sameas the x-axis shift assembly or shift system 140 shown in FIGS. 9 and 10and described above, and is therefore not further described orillustrated here. However, rather than the end fork air cylinder 152used in the x-axis shift system 140, the x-axis shift assembly 652 inthe indexer 600 has a pallet lift electric motor 654, for better controlof pallet lift movement.

The operation and sequencing of the indexer 600 is similar to that ofthe indexer 72 described above with reference to FIGS. 8-12. However,pallet movement along the y-axis is achieved via the computer controller85 controlling the y-axis drive motor 680 to incrementally move, orindex, the belts 670. During movement in the y-axis, the pallets 710remain on the belts 670 and rollers 676. As a result, unlike the indexer72, in the indexer 600, shown in FIGS. 30 and 31, there is no verticalmovement of pallets 710, as the pallets move in the y-axis direction,between pallet stations.

X-axis movement of the pallets 710 at the ends of the indexer 600, issimilar to the movement described above for the indexer 72 and istherefore not further described here.

At each pallet position, the optical sensor 72 detects the presence orabsence of a pallet 710 via detecting the presence or absence ofreflected light. In addition, at each pallet position A-J, the x-axissensor pair 690 detects the presence or absence of a cassette 88.Specifically, the infrared transmitter 692 projects a light beamvertically upwardly. The light beam passes through the x-axistransmitter prism 714, on each pallet 710, which bends the light beam90°, so that the light beam is then projected horizontally inwardlytowards the x-axis detector prism 716. If a cassette 88 is present onthe pallet 710, the light beam will be blocked by the cassette 88, andthe x-axis detector 694 will not detect any infrared light, indicatingpresence of a cassette 88. On the other hand, if the pallet 710 has nocassette 88 on it, infrared light from the transmitter 692 passesthrough the x-axis transmitter prism 714, passes over the pallet 710,and is redirected downwardly by the x-axis detector prism 716, so thatthe infrared light is directed to and detected by the x-axis infrareddetector 694, indicating the absence of a cassette 88.

The y-axis sensor pair 696 works in a similar way, to detect thepresence or absence of wafers in the cassette 88. With a cassette 88 ona pallet 710, infrared light from the yaxis transmitter 698 is projectedvertically upwardly, and is turned 90° by the y-axis transmitter prism718, so that the light projects through a slot or tunnel 725 at thebottom of the cassette 88. If no wafers or other flat media are presentin the cassette 88, the light travels entirely through the tunnel 75, isredirected downwardly by the y-axis detector prism 720, and is detectedby the y-axis detector 700, indicating absence of any wafers in thecassette 88. If a wafer is in the cassette 88, the bottom edge of thewafer projects downwardly through the tunnel 725, preventing light frompassing through the tunnel. Accordingly, the presence of any wafer inthe cassette 88 will block the light from the y-axis transmitter 698, sothat the y-axis detector 700 detects no light, indicating presence of atleast one wafer in the cassette 88.

Operation of the buffer assembly 618 in the indexer 600 is similar tooperation of the buffer assembly 76, described above, and shown in FIG.8. However, locating the buffer assembly 618 at the side of the indexer600 allows for a more compact design. Use of the belts 670 provides forfaster and more reliable pallet movement, in contrast to the indexer 72shown in FIGS. 8-16. Use of the prisms 714-720 allows for detection ofcassettes and wafers, without requiring lifting of the pallets.

Thus, a novel automated semiconductor processing system has been shownand described. Various changes can of course be made without departingfrom the sprit and scope of the invention. The invention, therefore,should not be limited, except by the following claims and theirequivalents.

What is claimed is:
 1. A machine for processing flat media articles,comprising: an enclosure; an indexer within the enclosure, the indexercomprising: an x-axis shift assembly; and a y-axis shift assemblyincluding first and second pairs of belts having a plurality of teeth; amotor linked at least indirectly to the first and second pairs of belts,for driving the first and second pairs of belts simultaneously inopposite directions; and a plurality of pallets supported at leastpartially on the belts with a plurality of teeth projecting from abottom surface of each pallet, for engaging the teeth on the first andsecond pair of belts.
 2. The machine of claim 1 further comprising aplurality of spaced apart rollers supporting the first and second pairsof belts, the rollers having flanges extending upwardly above the belts,and with the pallets supported at least partially on the flanges of therollers.
 3. The machine of claim 2 with the roller flanges extendinginto grooves in the pallets, to restrict pallet movement perpendicularto the belts.
 4. The machine of claim 1 wherein each of the beltsextends continuously through a plurality of indexer stations, andwherein the pallets are movable on the belts between indexer stationswithout lifting the pallets off of the belts.
 5. The machine of claim 1further comprising a buffer assembly attached to one side of theindexer, and a buffer drive motor linked to the buffer assembly, formoving the buffer assembly in a horizontal direction parallel to thebelts of the y-axis shift assembly.
 6. The machine of claim 5 whereinthe buffer assembly comprises a buffer plate attached to the indexer, abuffer slide rail attached to the buffer plate, and a buffer trayslidably supported on the buffer guide rails.
 7. The machine of claim 1further comprising a pair of prisms on at least one of the pallets. 8.The machine of claim 1 further comprising a first station in the indexerunder the first pair of belts, a first sensor pair in the first station,and a first prism pair on at least one of the pallets.
 9. The machine ofclaim 8 further comprising a pallet sensor in the first station, fordetecting the presence of a pallet at the first station.
 10. The machineof claim 9 further comprising a second sensor pair in the first station,and a second prism pair on the at least one pallet, with the secondprism pair oriented on a second line and the first prism pair orientedon a first line, with the second line perpendicular to the first line.11. The machine of claim 1 further comprising a pallet lifter in thex-axis shift assembly for lifting a pallet up off of the first pair ofbelts and for lowering the pallet onto the second pair of belts.
 12. Thesystem of claim 1 where the belts are endless toothed belts, with theteeth on the first and second pairs of endless toothed belts facingoutwardly.
 13. The system of claim 12 with each pallet including atoothed rack on a bottom surface for engaging the teeth on the first andsecond pairs of endless toothed belts.
 14. A machine for processing flatmedia, comprising: an enclosure; at least one process chamber within theenclosure; an indexer frame within the enclosure; at least one toothedbelt within the indexer frame; a motor linked to the at least onetoothed belt; a pallet supported at least partially on the toothed belt,the pallet having a toothed rack meshed with the at least one toothedbelt, and with the pallet having an opening through it; an elevator forraising and lowering a platform through the opening of the pallet; and aprocess robot within the enclosure for carrying flat media between theindexer frame and the at least one process chamber.
 15. A machine forprocessing flat media, comprising: an indexer; a y-axis shift system inthe indexer; a plurality of pallets supported on the y-axis shiftsystem; a first prism pair on at least one of the pallets; and a firstsensor pair aligned with the first prism pair.
 16. A machine for storingand handling flat media held in cassettes supported on pallets,comprising: a first-axis shift system for moving the pallets in a firstdirection; a second-axis shift system for moving the pallets in a seconddirection perpendicular to the first direction; a plurality of palletstations aligned with at least one of the first-axis and the second-axisshift systems; a pallet sensor at substantially each of the palletstations; a cassette sensor at substantially each pallet station; a flatmedia sensor at substantially each pallet station; a pair of cassettesensor prisms on substantially each pallet; and a pair of flat mediasensor prisms on substantially each pallet.
 17. A method of handlingflat media comprising the steps of: placing a cassette holding flatmedia onto a pallet; placing the pallet onto a specific location on afirst belt in an indexer; indexing the first belt and incrementallymoving the pallet in a first direction from a first pallet station to asecond pallet station within the indexer, with the pallet continuouslyremaining on the first belt; lifting the pallet vertically off of thefirst belt; moving the pallet in a direction perpendicular to the firstdirection, into a position over a second belt; lowering the pallet ontoa specific location on a second belt; and indexing the second belt andincrementally moving the pallet in a second direction, opposite to thefirst direction, with the pallet continuously remaining on the secondbelt.
 18. The method of claim 17 where the pallet is raised and loweredby substantially equivalent distances.
 19. A flat media processingsystem comprising: an enclosure; at least one process chamber within theenclosure; an indexer within the enclosure, the indexer comprising: anx-axis shift assembly; a y-axis shift assembly including a first pairand a second pair of belts; a motor linked at least indirectly to thefirst and second pairs of belts for driving the first and second pairsof belts simultaneously in opposite directions; a plurality of palletssupported at least partially on the first and second pairs of belts; anda process robot within the enclosure for carrying the semiconductorarticles between the indexer and the at least one process chamber.
 20. Aflat media processing system comprising: an enclosure; at least oneprocess chamber within the enclosure; an indexer within the enclosure;and a transfer robot for moving flat media from the indexer to the atleast one process chamber; the indexer comprising: a y-axis shiftassembly including first and second pairs of belts; a motor linked atleast indirectly to the first and second pairs of belts for driving thefirst and second pairs of belts in opposite y-axis directions; aplurality of pallets supported at least partially on the first andsecond pairs of belts; an x-axis shift assembly including first andsecond pallet lifters, for lifting pallets up and off the first andsecond pairs of belts, respectively; and a lateral drive motor linked atleast indirectly to the first and second pallet lifters for driving thefirst and second pallet lifters in directions perpendicular to they-axis.
 21. a The semiconductor article processing system of claim 20,wherein the first and second pairs of belts are endless toothed belts,the teeth on the first and second pairs of endless toothed belts facingoutward, with each pallet including a toothed rack on a bottom surfacefor engaging the teeth on the first and second pairs of endless toothedbelts.
 22. The processing system of claim 20, wherein the first andsecond pallet lifters move simultaneously in opposite directions.
 23. Amachine for processing flat media comprising: a first shift assembly inthe indexer for indexing pallets in a first direction; a second shiftassembly in the indexer for indexing pallets in a second direction,perpendicular to the first direction; a plurality of pallets supportedon and indexable by the first shift assembly; a first transmitter andfirst detector attached to the indexer, and a first transmitter prismand a first detector prism on at least one of the pallets and alignedwith each other in the second direction, the first transmitter prism onthe pallet optically aligned with the first transmitter and the firstdetector prism on the pallet optically aligned with the first detector,wherein the pallet containing the first transmitter prism and the firstdetector prism is detected by the first transmitter and first detector,when the first transmitter prism and first detector prism are alignedwith the first transmitter and first detector.
 24. The first machine ofclaim 23 wherein the first transmitter, first detector, firsttransmitter prism, and first detector prism detect the presence orabsence of a flat media article contained within a cassette on thepallet.
 25. The machine of claim 23 further including a pallet sensorfor detecting the presence or absence of a pallet at a pallet positionon the indexer.